My machine is running in server only, behind a router which forwards the port I need using Virtual Server. From other posts it seems like telnet is disabled by default, but that has to do with shell access though, but maybe this could affect that I’m not able to connect using “outside” IP.
As for telnet not being secure, it’s not that big a deal for the service I need, I was more concerned about allowing it for this particular service only (if possible)